| In order to protect elver resources in our country,and to solve the obstruction effect of low-head water-power engineering on the back migration of the elvers,and provide suggestions for the construction of eels'fishway in China.Based on the indoor monitor data from March2017 to September 2017,this paper uses video,statistics,physical models and computational fluid dynamics numerical calculation methods to systematically analyze the selectivity and activity of carp on light color,the behavior characteristics of the eels and the success rate of the eels under different hydrodynamic conditions.The flow pattern,flow velocity and turbulent kinetic energy in the entrance and chamber of fishway under different channel arrangement forms.The main conclusions are as follows:1.The entrance phototaxis showed that the juvenile eels phase is more sensitive to the longer wavelength red and yellow light,and the blue and green light with shorter wavelength is low selectivity.The juvenile eels has strong persistence to red,yellow and purple light,but not to other light colors,and red light and purple light have less visual irritating effect on fish,and have the effect of attracting fish for a long time.Although yellow light also has a strong effect of attracting fish,it is more irritating to eels'eyes.There is a period of fatigue,which is not suitable for attracting fish for a long time.2.The Physical model tests show that when plum-blossom matrix is set on weir surface,the matrix interval is h=1.5 times,the bottom slope is less than 30°and the flow rate per unit width is less than 9.7×10-4 m3/s.m,the eel back migration effect is better,and the success rate is increased from 11%to the original control group to 91.67%.And compared to the control group,the elvers of the experimental group are more active in the process of back migration and its form is similar to the snake crawling,which shows S,Z and straight type.Besides,the edge-oriented movement is more obvious,which is a typical kind of behavior of climbing the top of a weir though a typical burst swimming events,which maximum explosive speed reaches up to 0.66 m/s.3.The numerical simulation based on computational fluid dynamics?CFD?shows thatt when the single-width flow is 9.7×10-4 m3/s·m,the maximum inlet current velocity is 0.45 m/s,and the surface recirculation area accounts for about 1/3 of the inlet area.At the same time,the turbulent kinetic energy and turbulent energy dissipation rate are large.The water flow conditions are more confusing and can provide a better attraction flow for the eels,which is the ideal entrance for the eels'fishway.The Weir Surface's velocity ranges from 0.2 to 0.6 m/s and occupy about 2/3 of the simulated area.This condition is more suitable for inducing fish to pass through the surface,reducing the swimming consumption of the eels and ensuring the stability in the process of back migration,so that the eels successfully enters the upstream. |
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